Mixed basic metal oxide/sulfide catalyst

ABSTRACT

A mixed basic metal oxide/sulfide catalyst having the formula 
     
         xA.yB.zC.qD 
    
     wherein A is an alkali metal selected from lithium, sodium, potassium, rubidium, cesium and mixtures thereof; B is a cation which has an ionization state 2 and 3 greater than the ionization state of C; B is selected from titanium, zirconium, hafnium, tantalum, niobium, vanadium and mixtures thereof; C is selected from magnesium, calcium, strontium, barium and mixtures thereof; D is selected from oxygen, sulfur and mixtures thereof; x and y are in mole fractions of z such that when z=1 then x=0.001 to 0.25, and y=0.001 to 0.25; and q is a number necessary to maintain charge balance with D. The sulfide form provides tolerance for sulfur containing feedstocks. The catalyst is useful for oxidative coupling of methane and aliphatic and alicyclic hydrocarbon compounds with an aromatic compound to produce higher molecular weight hydrocarbons and for dehydrogenating hydrocarbon compounds to produce unsaturated aliphatic and alicyclic chains.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to mixed basic metal oxide/sulfide catalystsuseful for production of higher hydrocarbons by oxidative coupling ofmethane, production of higher hydrocarbons by oxidative coupling ofaliphatic and alicyclic hydrocarbon compounds with aliphatic andalicyclic substituted aromatic hydrocarbon compounds to form a longersubstituent hydrocarbon on the aromatic ring, and production ofunsaturated aliphatic and alicyclic chains by dehydrogenation ofaliphatic and alicyclic hydrocarbon compounds and aliphatic andalicyclic substituted aromatic hydrocarbon compounds. Reaction ofmethane with oxygen in the presence of a mixed basic metal oxide/sulfidecatalyst in accordance with this invention results in high conversion ofmethane with selectivity for ethane and ethylene products. Reaction ofmethane with toluene and oxygen in the presence of a mixed basic metaloxide/sulfide catalyst according to this invention results in highconversion to form styrene. One important dehydrogenation is thereaction of ethylbenzene in the presence of a mixed basic metaloxide/sulfide catalyst according to this invention to produce styrene.

2. Description of the Prior Art

Methane is currently available in large quantities from natural gas,anaerobic digestion of organic material, and chemical processingsources. However, use of methane as a chemical feedstock has beenlimited due to its high stability. It has been highly desirable todevelop a catalyst for such reactions to enable operation under milderconditions with greater control over thermodynamic and kinetic processesas well as provide product selectivity and high reaction rate.

Oxidative coupling of methane to form higher hydrocarbons has been shownto be effected over a number of metal oxides, but yields of desiredproducts have been low, as discussed by Keller, G. E. and M. M. Bhasin,J. of Catalysis 73, 9-19 (1982). Sodium and lead on alumina has beenfound to catalyze the formation of ethane and ethylene from methane, asdisclosed in Hinsen, W. and M. Baerns, Chem.-Ztg., 107, 223-226 (1983)and Hinsen, W., W. Bytyn and M. Baerns, Proc. 8th Int. Congr. Catal.,Berlin, III 581-592 (1984). Several U.S. patents teach a series ofsupported metal oxides which while effective for the conversion ofmethane to ethane and ethylene, are based on reducible metal oxides andused in a stoichiometric fashion by alternately exposing them to anoxidizing atmosphere and then to methane in the absence of oxygen. U.S.Pat. Nos. 4,443,644; 4,443,645; 4,443,646; 4,443,647; 4,443,648;4,443,649; 4,444,984, 4,499,322; 4,499,323; 4,499,324; and 4,523,049.

Later work has demonstrated that magnesium oxide and calcium oxide, whenpromoted with alkali metal salts, are active for oxidative coupling ofmethane to ethane and ethylene in the presence of oxygen. See Kimble,James B. and John H. Kolts, "Oxidative Coupling of Methane to HigherHydrocarbons", Energy Progress, Vol. 6, p. 227 (1986); Driscoll, D. J.,W. M. Martir, J. Wang and J. H. Lunsford, J. Am. Chem. Soc. 107, 58-63(1985); and Ito, T., J. Wang, C. Lin and J. H. Lunsford, J. Am. Chem.Soc. 107, 5062-64 (1985). These later Catalysts have the advantage ofoperating continuously, not requiring regeneration or pretreatment.

Borates and boron compounds have been used in partial oxidation ofhydrocarbons, such as boric acid to oxidize long chain normal paraffinsin the liquid phase (Illingworth, G. F. and G. W. Lester, ACS PetroleumDivision Preprints, 12, No. 3, 161 (1967)) and oxidation of n-dodecanein the liquid phase to the corresponding alcohol (Lee, K. W., M. J.Choi, S. B. Kim and C. S. Choi, Ind. Eng. Chem. Res. 26, 1951 (1987)).Boric acid has been used by coating reactor walls in the combustion ofmethane to eliminate free radical destruction at temperatures of lessthan 513° C. (Kegeyan, E. M., I. S. Vardanyan and A. B. Nalbandyan,Kinetics and Catalysis 17, No. 4,749-754 and No. 4,755-759 (1976))

A number of publications describe oxidative methylation of tolueneperformed in Russia: Chemical Abstracts 97:127153K (I982) teachesnon-catalytic methylation of toluene depended mostly on pressure andPhMe/O/CH₄ molar ratio; Chemical Abstracts 99:70137t (1983) teachesoxidative methylation of toluene using a Ni-V oxide or V oxide catalyst;Chemical Abstracts 101:74734t (1984) teaches oxidative methylation oftoluene in presence of oxygen (max. 15 percent in reaction mixture)results in products including styrene; Chemical Abstracts 101:38205 n(1984) teaches simultaneous production of styrene, ethylbenzene,benzene, and phenols by reaction of toluene with C₁₋₄ alkanes in thepresence of oxygen and Fe₂ O₃ or TiO₂ at 600-800°. Productivityincreased at higher pressure in presence of H₂ O₂ and/or (Me₃ C)₂ O₂ ;and U.S. Pat. No. 3,830,853 teaches reaction of toluene with a lowerparaffin hydrocarbon in the presence of oxygen at 600°-900° C. and spacevelocity of 2000-10000 hour⁻¹.

Styrene is an important commercial unsaturated aromatic monomer usedextensively in the manufacture of plastics by polymerization andcopolymerization. On a commercial scale, the great majority of theworld's styrene is produced by dehydrogenation of ethylbenzene. A reviewof styrene synthesis processes is given in Kirk-Othmer, Encyclopedia ofChemical Technology, Third Edition, Vol. 21, Styrene, pgs. 770-801. Onecommercial process for production of styrene is the UOP Styro-Plusprocess using ethylbenzene and superheated steam under vacuum for thecatalytic dehydrogenation of ethylbenzene as taught by Ward, D. J. etal, Hydrocarbon Processing, Vol. 66, No. 3, March 1987, pgs 47-48. Useof cokecovered alumina and boron/alumina catalysts for oxidativedehydrogenation of ethylbenzene is taught by Fiedorow, R., W.Przystajko, M. Sopa and I. G. Dalla Lana, The Nature and CatalyticInfluence of Coke on Alumina: Oxidative Dehydrogenation of Ethylbenzene,Journal of Catalysis 68, pgs. 33-41 (1981). Oxidative dehydrogenation ofethylbenzene to styrene over metal pyrophosphates, such as cerium, tin,zirconium, and titanium phosphates and calcium magnesium, strontium,barium, nickel, aluminum, thorium, zinc and silicon phosphates is taughtby Vrieland, G. E., Oxydehydration of Ethylbenzene to Styrene over MetalPhosphates, Journal of Catalysis 111, pgs. 1-13 (1988). This articleteaches the condensed phosphate surface is the dominant factor as acatalyst and that the cation has little or no effect.

SUMMARY OF THE INVENTION

This invention provides a mixed basic metal oxide/sulfide catalyst andcatalytic process for oxidative coupling of methane to produce highermolecular weight hydrocarbons. The catalysts of this invention include ametal cation which has an ionization state 2 and 3 greater than theionization state of a second metal cation present in the catalyst.

A mixed basic metal oxide catalyst including a metal cation which has anionization state 1 greater than the ionization state of a second metalcation present in the catalyst and its use for oxidative coupling ofmethane is fully described in copending and commonly owned U.S. patentapplications, Mixed Basic Oxide Catalyst for Oxidative Coupling ofMethane, Ser. No. 07/172,808, filed Mar. 28, 1988, now U.S. Pat. No.4,826,796, and Mixed Basic Metal Oxide Catalyst for Oxidative Couplingof Methane, Serial No. 07/274,415, filed Nov. 21, 1988. Oxidativecoupling of aliphatic and alicyclic hydrocarbons with aliphatic andalicyclic substituted aromatic hydrocarbons using the same mixed basicmetal oxide catalyst including a metal cation having an ionization state1 greater than a second metal cation in the catalyst is fully describedin copending and commonly owned U.S. patent application, OxidativeCoupling of Aliphatic and Alicyclic Hydrocarbons With Aliphatic andAlicyclic Substituted Aromati Hydrocarbons, Ser. No. 07/274,454, filedNov. 21, 1988. Dehydrogenation of saturated hydrocarbon chains using thesame mixed basic metal oxide catalyst is fully described in copendingand commonly owned U.S. patent application, Dehydration of Aliphatic andAlicyclic Hydrocarbons and Aliphatic and Alicyclic Substituted AromaticHydrocarbons, Ser. No. 07/274,499, filed Nov. 21, 1988. A mixed basicmetal sulfide catalyst in which one metal cation has an ionization state1 greater than the ionization state of a second metal cation and its usein the above processes is described in copending and commonly owned U.S.patent application, Mixed Basic Metal Sulfide Catalyst, Ser. No.07/359,207, filed May 31, 1989. The above copending commonly owned U.S.patent applications are fully incorporated herein by reference.

The mixed basic metal oxide/sulfide catalyst of this invention has theformula:

    xA.yB.zC.qD

wherein A is an alkali metal selected from lithium, sodium, potassium,rubidium, cesium and mixtures thereof, preferably lithium; B is a cationwhich has an ionization state 2 and 3 greater than the ionization stateof C; B is selected from titanium, zirconium, hafnium, tantalum,niobium, vanadium, and mixtures thereof, preferably titanium andtantalum; C is selected from magnesium, calcium, strontium, barium andmixtures thereof; preferably magnesium; D is selected from oxygen andsulfur and mixtures thereof; x and y are in the mole fractions of z suchthat when z=1 then x=0.001 to 0.25, preferably 0.05 to 0.15 and y=0.001to 0.25, preferably 0.002 to 0.20; and q is a number necessary tomaintain charge balance with D.

The above mixed basic metal oxide/sulfide catalyst may be used in pureoxide form or pure sulfide form and in any mixture of oxides andsulfides. The sulfide form provides sulfur tolerance to feedstockscomprising sulfur compounds, such as H₂ S.

This invention provides a catalyst for oxidative coupling of methane toproduce a higher molecular weight hydrocarbon and for oxidative couplingof aliphatic and alicyclic hydrocarbon compounds with aliphatic andalicyclic substituted aromatic hydrocarbon compounds to produce a longersubstituent hydrocarbon on the aromatic ring. The reaction of analiphatic or alicyclic hydrocarbon compound with an aliphatic oralicyclic substituted aromatic hydrocarbon compound and oxygen isconducted in the presence of a mixed basic metal sulfide catalyst atelevated temperature according to the following general reaction:##STR1## wherein R is an aliphatic or alicyclic hydrocarbon radical; andR' is an aliphatic or alicyclic hydrocarbon radical substituted on anaromatic hydrocarbon ring.

It is unexpected that catalysts active for oxidative coupling asdescribed above involving carbon-carbon bond formation would also beactive for dehydrogenation involving carbon-hydrogen bond breaking withsubsequent carbon-carbon double bond formation. Dehydrogenation ofsaturated organics has been described by Thomas, Charles L, CatalyticProcesses and Proven Catalysts, Chap. 6, Dehydrogenation, pgs. 41-45,Academic Press (1970).

This invention provides a catalyst and process for dehydrogenation ofaliphatic and alicyclic chains of aliphatic and alicyclic hydrocarboncompounds and aliphatic and alicyclic substituted aromatic hydrocarboncompounds to produce an unsaturation in the hydrocarbon chain. Thereaction of an aliphatic or alicyclic hydrocarbon compound, an aliphaticor alicyclic substituted aromatic hydrocarbon compound and mixturesthereof in the dehydrogenation reaction is conducted in the presence ofa mixed basic metal oxide/sulfide catalyst at elevated temperature. Thedehydrogenation may proceed directly according to the following generalreaction of C--C bonding in a compound RH or R'CH₃ being converted toC═C bonding+H₂ or may proceed by oxidative dehydrogenation wherein C--Cbonding in a compound RH or R'CH₃ +1/2O₂ is converted to C═C bonding+H₂O, wherein R is an aliphatic or alicyclic hydrocarbon radical having 2and more carbon atoms; and R' is an aliphatic or alicyclic hydrocarbonradical substituted on an aromatic hydrocarbon ring. In the case ofdehydrogenation of ethylbenzene to styrene according to this invention,direct dehydrogenation proceeds according to the general reaction:##STR2## and by partial oxidation or oxidative dehydrogenation accordingto the general reaction: ##STR3## The mixed basic metal sulfide catalystof this invention provides a catalyst which is tolerant of sulfurcontaining reactant compounds. Such sulfur tolerance is important whenusing hydrocarbon reactants derived from natural sources, such asmethane obtained from gasification of coal, shale, and other naturalcarbonaceous materials. The maintenance of catalytic activity of themixed basic metal sulfide catalyst of this invention in the presence ofsulfur containing materials, such as H₂ S, is of great commercialimportance in view of the high cost of sulfur removal from hydrocarbonsderived from naturally occurring sources.

DESCRIPTION OF PREFERRED EMBODIMENTS

The catalyst of this invention is a mixed basic metal oxide/sulfidecatalyst having the formula xA.yB.zC.qD wherein A, B, C, D, x, y, z andq have the meanings set forth above. In the catalyst formulation, B is apromoter on a C matrix to enhance active component A. The catalysts ofthis invention have metal cations with an oxidation state besides themetal, of +4 and +5 which modify a +2 oxidation state matrix to promotethe desired product selectivity.

The mixed basic metal oxide/sulfide catalyst of this invention may beused in its pure oxide or pure sulfide form or may be used in admixture.When sulfur containing hydrocarbon feedstocks are used in the reactionscatalyzed, it is preferred that the sulfide catalyst comprise over about50 percent by weight of the total sulfide and oxide catalyst, and mostpreferably about 75 to about 100 percent. The mixed sulfide and oxidecatalyst comprises mixed basic metal sulfide having the formula:xA.yB.zC.qS, wherein A is an alkali metal selected from lithium, sodium,potassium, rubidium, cesium and mixtures thereof; B is a cation whichhas an ionization state 2 and 3 greater than the ionization state of C;B is selected from titanium, zirconium, hafnium, tantalum, niobium,vanadium and mixtures thereof; C is selected from magnesium, calcium,strontium, barium and mixtures thereof; x and y are in mole fractions ofz such that when z=1 then x=0.001 to 0.25, and y=0.001 to 0.25; and q isa number necessary to maintain charge balance with S being sulfur; inadmixture with mixed basic metal oxide having the formulax'A'.y'B'.z'C'.q'O wherein A' is an alkali metal selected from lithium,sodium, potassium, rubidium, cesium and mixtures thereof; B' is a cationwhich has an ionization state 2 and 3 greater than the ionization stateof C'; B' is selected from titanium, zirconium, hafnium, tantalum,niobium, vanadium and mixtures thereof; C' is selected from magnesium,calcium, strontium, barium and mixtures thereof; x' and y' are in molefractions of z' such that when z'=1 then x'=0.001 to 0.25, and y'=0.001to 0.25; and q' is a number necessary to maintain charge balance with 0being oxygen.

The mixed basic metal oxide/sulfide catalyst of this invention may beprepared by making a liquid solution of one or two soluble compounds ofdesired metal or metals or a colloidal suspension of solids in theliquid and adding it to a metal oxide or sulfide or mixed oxide/sulfidepowder of the remaining component or components. Any liquid solutionswhich will retain the desired oxide or sulfide form of the metalcompound are satisfactory. A wide variety of non-interfering ions may beused to form suitable liquid soluble compounds as long as they do notcause undesired chemical interference. Suitable such compounds includeacids, sulfides, oxides, hydrides, nitrates, carbonates, and hydroxides.The liquid solution or colloidal suspension of one or two components isadded to metal oxide/sulfide powder of the remaining component orcomponents and well mixed followed by drying at a sufficient temperatureand for a sufficient time to expel volatile components. The mixture isthen crushed and sieved to a small size for catalytic use. Conventionaland well known catalyst manufacturing techniques may be employed toproduce the catalyst material described above. When preparing thesecatalytic materials, it is preferred to employ manufacturing techniquesresulting in a product having a substantially uniform or homogeneouscomposition. Shaping of the material may be effected according toconventional techniques of the art, particularly tableting, or pelletingor extrusion. The catalyst may be used unsupported or alternatively itmay be supported on an inert support as known to the art, such asalumina, silica, activated carbon and the like.

A preferred catalyst may be prepared by mixing a water soluble compoundof tantalum, such as tantalum oxalate, tantalum ethoxide, or lithiumtantalate and a water soluble salt of the alkali metal promoter, such asnitrate, carbonate, hydroxide, or water soluble ion with stirring toobtain complete solution of the solids. The aqueous solution of tantalumand alkali metal is added to the metal oxide powder with stirring toobtain a homogeneous mixture which may then be dried at a temperature inexcess of about 110° C. The dried mixture may then be calcined at atemperature of 700° to 750° C. for a sufficient time, about 2 hours, toexpel volatile portions. The mixture is then crushed and sieved to anappropriately small mesh size of about -6 to about +40, preferably about-12 to about +20 for use as a catalyst.

This invention provides gas phase oxidative coupling of methane byreaction of methane and oxygen in the presence of the above describedmixed basic metal oxide/sulfide catalyst, such as a tantalum/alkalimetal promoted metal oxide/sulfide catalyst. Feedstock gas comprisingmethane suitable for use in the process of this invention may compriseany methane containing gas which does not contain interfering compounds.Preferably, the methane containing gas used in the process of thisinvention comprises about 25 mole percent up to about 100 mole percentmethane. Suitable sources of methane containing gas include natural gas,synthetic natural gas (SNG), product gas from gasification ofcarbonaceous materials, such as gasification of coal, peat, shale, andthe like, as well as products of anaerobic digestion of various biomassmaterials. These gases principally comprise methane and may containother hydrocarbon gases such as ethane and propane which may producecorresponding chemical reactions to those of methane in the process ofthis invention. Purification of such mixed gases comprising principallymethane is not usually necessary, especially when using the sulfurtolerant basic metal sulfide catalyst of this invention. These sourcesof methane containing gas and processes for producing methane are wellknown in the art. The term "methane" as used throughout this disclosureand claims refers to methane as described above.

Any oxygen containing gas not containing interfering chemical compoundsis useful as a feedstock in oxidative coupling according to thisinvention. The term "oxygen containing gas" as used throughout thisdisclosure and claims, refers to gas containing oxygen, such as air andgases having an oxygen content of up to 100 percent. It is preferred touse oxygen containing gas comprising over 50 volume percent oxygen. Themole percentage of oxygen relative to the mole percentage of methane inthe gas mixture subjected to the process of this invention is about 2 toabout 40 and preferably about 5 to about 20 mole percent oxygen.

The catalyst may be placed into a reactor, such as a tube-shell fixedbed, fluidized bed, moving bed, inter-bed heat exchange type,Fischer-Tropsch type, or other reactor type known to the art. Suitablereactor vessels for use at the desired operating temperatures andpressures are well known to the art. The reaction of methane and oxygenaccording to this invention is carried out by passing a gaseous mixturecomprising methane and oxygen over the mixed basic metal oxide/sulfidecatalyst as defined above at about 500° to about 1100° C., preferablyabout 600° to about 900° C. Suitable gas residence times are about 0.002to about 0.00002 hour preferably about 0.0005 to about 0.0001 hour. Thereaction may be carried out at about pressures of about 1 to about 1515psia, preferably about 1 to about 150 psia.

The catalyst of this invention provides a longer hydrocarbon substituenton an aromatic ring by gas phase oxidative coupling of saturated carbonatoms of an aliphatic or alicyclic hydrocarbon compound with analiphatic or alicyclic substituted aromatic hydrocarbon and oxygen.Suitable aliphatic and alicyclic hydrocarbon compounds for use asfeedstocks in the process of this invention include straight andbranched chain saturated and unsaturated aliphatic hydrocarbons, such asmethane, ethane, propane, butane, heptane, pentane, hexane, octane,isobutane, isohexane, isooctane, 1-pentene, 1-hexene and mixturesthereof; cyclic chain saturated and unsaturated alicyclic hydrocarbons,such as cyclobutane, cycloheptane, cycloheptene, cyclohexane,cyclohexene and mixtures thereof; and aryl substituted aliphatic andalicyclic hydrocarbons, such as toluene, xylene, mesitylene, durene,cumene and mixtures thereof. In the case of unsaturated hydrocarbons, itshould be noted that the oxidative coupling of this invention does notoccur at the unsaturated bonding. Suitable aliphatic and alicyclicsubstituted aromatic hydrocarbon compounds for use as feedstocks in thisinvention are aromatic ring hydrocarbons having at least one aliphaticor alicyclic hydrocarbon radical substituent on the aromatic ring, suchas toluene, xylene, indan, tetralin, and mixtures thereof.

The reactants are fed to the reaction zone in mole percent proportionsof about 50 to about 90 mole percent aliphatic or alicyclic hydrocarboncompounds, preferably about 75 to about 85 mole percent; about 2 toabout 40 mole percent substituted aromatic hydrocarbon, preferably about5 to about 15 mole percent; and about 2 to about 20 mole percent oxygen,preferably about 5 to about 12 mole percent. Steam may be added in anamount of up to about 1 mole of steam per mole hydrocarbon to inhibitdeep oxidation. Steam does not enter into the reaction but solely actsas an oxidation inhibitor. It is preferred to use oxygen containing gascomprising over 50 volume percent oxygen. The amounts of oxygen used inthe oxidative coupling of aliphatic and alicyclic hydrocarbons witharomatic hydrocarbons are expressed as pure oxygen. The oxygencontaining gas may be preheated by thermal exchange with the catalystbed to a temperature suitable for the reaction controlling step of theprocess. An important aliphatic feedstock suitable for use in theprocess of this invention may comprise methane as described above.Important substituted aromatic feedstocks include toluene and xyleneavailable from commercial sources.

The oxidative coupling is carried out by passing the gaseous aliphaticor alicyclic hydrocarbon and aromatic feedstocks and oxygen over themixed basic metal oxide/sulfide catalyst as defined above at about 300°to about 1100° C., preferably about 600° to about 900° C. Suitable gasresidence times are about 0.002 to about 0.00002 hour preferably about0.0005 to about 0.0001 hour with space velocity of about 500 to about50,000 vol/vol/hr, preferably about 1000 to about 5000 vol/vol/hr. Thereaction may be carried out at about pressures of about 1 to about 1515psia, preferably about 1 to about 150 psia, pressures above atmosphericmay enhance the rate of reaction. Suitable reactor vessels for use atthe above operating temperatures and pressures are well known to theart. The products of the single reactor used in the process of thisinvention may be passed to a simple separator for separation of thehydrocarbon product, condensate, and vent gas.

One important oxidative coupling reaction according to the process ofthis invention is the production of styrene directly by coupling oftoluene and methane by the following reaction in the presence of theabove defined catalyst: ##STR4## At 750° C. the heat of reaction (ΔH) is-73 kcal/mole and the sensible heat plus the heat of vaporization oftoluene is about 55 kcal/mole. Thus the process operates close toautothermal conditions after initial light-off. Conventional processesusing Fe₂ O₃ as a catalyst with Cr₂ O₃ as a stabilizer and K₂ CO₃ as acoke retardant for production of styrene require ethylbenzene feedstock,produced from expensive benzene and ethylene and require large amountsof superheated steam (800° C. and molar ratio 14 steam to 1ethylbenzene) due to the conversion of ethylbenzene to styrene beingendothermic. The process of this invention uses relatively inexpensivetoluene, methane and air as feedstock to a single reactor where bothstyrene and ethylbenzene are produced in a process that does not requiresuperheated steam.

The catalyst of this invention provides unsaturated aliphatic andalicyclic chains by dehydrogenation of saturated carbon atoms of analiphatic or alicyclic hydrocarbon compound and an aliphatic oralicyclic substituted aromatic hydrocarbon and mixtures thereof.Suitable aliphatic and alicyclic hydrocarbon compounds for use asfeedstocks in the process of this invention include straight andbranched chain saturated aliphatic hydrocarbons, such as ethane,propane, butane, heptane, pentane, hexane, octane, isobutane, isohexane,isooctane and mixtures thereof; cyclic chain saturated alicyclichydrocarbons, such as cyclobutane, cycloheptane, cyclohexane andmixtures thereof. Suitable aliphatic and alicyclic substituted aromatichydrocarbon compounds for use as feedstocks in this invention arearomatic ring hydrocarbons having at least one saturated aliphatic oralicyclic hydrocarbon radical substituent on the aromatic ring, such asethylbenzene, indan, tetralin and mixtures thereof.

The hydrocarbon reactant is fed to the reaction zone in contact with theabove defined mixed basic metal oxide/sulfide catalyst for directdehydrogenation and for oxidative dehydrogenation. For oxidativedehydrogenation oxygen may be added up to a mole amount of about 5 molesoxygen per mole hydro-carbon, preferably about 0.5 to about 2.0 molesoxygen per mole hydrocarbon. Steam may be added in an amount of up toabout 1 mole of steam per mole hydrocarbon to inhibit undesired sidereactions when oxygen is used in the feed for oxidative dehydrogenation.Steam does not enter into the reaction but solely acts as an oxidationinhibitor. For direct dehydrogenation, without oxygen in the feed, steammay be used as a heat carrying agent and up to 10 moles of steam permole of hydrocarbon may be required.

The dehydrogenation process according to this invention is carried outby passing the gaseous aliphatic or alicyclic hydrocarbon or aromaticfeedstock over the mixed basic metal oxide/sulfide catalyst as definedabove at a space velocity of about 500 to about 50,000 vol/vol/hrproviding gas residence times of about 0.002 to about 0.00002 hourpreferably about 0.000 to about 0.00007 hour. Suitable temperatures areabout 200° to about 1000° C., preferably about 600° to about 850° C. fordirect dehydrogenation and preferably about 450° to about 700° C. foroxidative dehydrogenation. The reaction may be carried out at pressuresof about 1 psia to about 1515 psia, preferably about 1 psia to about 25psia for direct dehydrogenation and preferably about 1 psia to about 150psia for oxidative dehydrogenation. Pressures above atmospheric mayenhance the rate of reaction. Suitable reactor vessels for use at theabove operating temperatures and pressures are well known to the art.The products of the single reactor used in the process of this inventionmay be passed to a simple separator for separation of the hydrocarbonproduct, condensate, and vent gas.

One important dehydrogenation reaction according to the process of thisinvention is the production of styrene directly by dehydrogenation ofethylbenzene or by oxidative dehydrogenation of ethylbenzene in thepresence of the above defined mixed basic metal oxide/sulfide catalystaccording to the reactions set forth above. At 727° C. the heat ofreaction (ΔH) for oxidative dehydrogenation is -29.4 kcal/moleexothermic and the sensible heat plus the heat of vaporization ofethylbenzene is about 33.0 kcal/mole. Thus the oxidative dehydrogenationprocess operates close to autothermal conditions after initiallight-off. Conventional processes for production of styrene fromethylbenzene feedstock require large amounts of superheated steam (800°C. and molar ratio 14 steam to 1 ethylbenzene) because the conversion ofethylbenzene to styrene is endothermic. The dehydration process of thisinvention uses a single reactor in a process that does not requiresuperheated steam.

The following specific examples are set forth in detail to illustratethe invention and should not be considered to limit the invention in anymanner.

EXAMPLE I

A mixed basic metal oxide catalyst was prepared having the formulation0.065 Li 0.056 Ti 1.0 Mg 1.09 O by mixing 3.00 grams LiNO₃, 1.15 gramsconcentrated HNO₃ and 50.52 grams of deionized water and stirred toobtain solution of the solids. The solution was slowly added over amixture of 3.00 grams TiO₂ (Degussa P25) and 27.00 grams MgO powder andmixed to obtain a slurry. The slurry was dried at 110° C. overnightfollowed by calcining at 800° C. for one hour. The dried solids mixturewas then crushed to a mesh size of -12 to +20.

Twelve grams of the above prepared catalyst was packed into a fixed bedand a gaseous feed of 60 volume percent methane and 40 volume percentair was passed through the bed at a space velocity of 4500-4600, 801° C.and 1 atmosphere pressure. Two runs were conducted with results as shownin the following Table:

                  TABLE I                                                         ______________________________________                                                        Selectivity SCC Ethane +                                      Conversion of   % Ethane +  Ethylene/gram                                     Methane %       Ethylene    catalyst-hour                                     ______________________________________                                        Run 1  10           33           66                                           Run 2  12           46          101                                           ______________________________________                                    

EXAMPLE II

In a similar manner a mixed basic metal oxide of the formulation 0.058Li 0.009 Ta 1.0 Mg 1.05 O was prepared by mixing 2.62 grams LiNO₃ and1.68 grams LiTaO₃ with 50.06 grams deionized water and stirred untilonly a small amount was not dissolved. The mixture was poured over 30.00grams MgO and stirred until a uniform slurry was obtained. The slurrywas dried at 110° C. overnight, calcined at 800° C. for one hour, andthe solids crushed to -12+20 mesh.

The prepared catalyst was loaded into a reactor and used as a methaneoxidative coupling catalyst under the same conditions as in Example Iresulting in 18 percent conversion of methane with 73 percentselectivity to ethane and ethylene. The rate of ethane+ethyleneformation was 200 SCC/gram catalyst-hour.

While in the foregoing specification this invention has been describedin relation to certain preferred embodiments thereof, and many detailshave been set forth for purpose of illustration, it will be apparent tothose skilled in the art that the invention is susceptible to additionalembodiments and that certain of the details described herein can bevaried considerably without departing from the basic principles of theinvention.

We claim:
 1. A mixed basic metal oxide/sulfide catalyst having theformula:

    xA.yB.zC.qD

wherein A is an alkali metal selected from lithium, sodium, potassium,rubidium, cesium and mixtures thereof; B is a cation which has anionization state 2 and 3 greater than the ionization state of C; B isselected from hafnium, tantalum, niobium, vanadium and mixtures thereof;C is selected from magnesium, calcium, strontium, barium, and mixturesthereof; D is selected from oxygen, sulfur and mixtures thereof; x and yare in mole fractions of z such that when z=1 then x=0.001 to 0.25, andy=0.001 to 0.25; and q is a number necessary to maintain charge balancewith D.
 2. A catalyst according to claim 1 wherein A is lithium, B istantalum and C is magnesium.
 3. A catalyst according to claim 1 whereinx=0.05 to 0.15 and y=0.002 to 0.20.
 4. A catalyst according to claim 1wherein A is lithium.
 5. A catalyst according to claim 1 wherein C ismagnesium.
 6. A catalyst according to claim 1 wherein A is lithium and Cis magnesium.
 7. A catalyst according to claim 1 wherein D is oxygen. 8.A catalyst comprising mixed basic metal sulfide having the formulaxA.yB.zC.qS, wherein A is an alkali metal selected from lithium, sodium,potassium, rubidium, cesium and mixtures thereof; B is a cation whichhas an ionization state 2 and 3 greater than the ionization state of C;B is selected from titanium, zirconium, hafnium, tantalum, niobium,vanadium and mixtures thereof; C is selected from magnesium, calcium,strontium, barium and mixtures thereof; x and y are in mole fractions ofz such that when z=1 then x=0.001 to 0.25, and y=0.001 to 0.25; and q isa number necessary to maintain charge balance with S being sulfur; inadmixture with mixed basic metal oxide having the formulax'A'.y'B'.z'C'.q'O wherein A' is an alkali metal selected from lithium,sodium, potassium, rubidium, cesium and mixtures thereof; B' is a cationwhich has an ionization state 2 and 3 greater than the ionization stateof C'; B' is selected from titanium, zirconium, hafnium, tantalum,niobium, vanadium and mixtures thereof; C' is selected from magnesium,calcium, strontium, barium and mixtures thereof; x' and y' are in molefractions of z' such that when z'=1 then x'=0.001 to 0.25, and y'=0.001to 0.25; and q' is a number necessary to maintain charge balance with 0being oxygen.
 9. A mixed sulfide and oxide catalyst according to claim 8wherein said mixed basic metal sulfide comprises greater than about 50weight percent of said catalyst.
 10. A mixed sulfide and oxide catalystaccording to claim 8 wherein said mixed basic metal sulfide comprisesabout 75 to 100 weight percent of said catalyst.
 11. A mixed basic metalsulfide catalyst having the formula:

    xA.yB.zC.qS

wherein A is an alkali metal selected from lithium, sodium, potassium,rubidium, cesium and mixtures thereof; B is a cation which has anionization state 2 and 3 greater than the ionization state of C; B isselected from titanium, zirconium, hafnium, tantalum, niobium, vanadiumand mixtures thereof; C is selected from magnesium, calcium, strontium,barium, and mixtures thereof; S is sulfur; x and y are in mole fractionsof z such that when z=1 then x=0.001 to 0.25, and y=0.001 to 0.025; andq is a number necessary to maintain charge balance with S.
 12. Acatalyst according to claim 11 wherein A is lithium, B is selected fromthe group consisting of titanium, tantalum and mixtures thereof and C ismagnesium.
 13. A catalyst according to claim 11 wherein x=0.05 to 0.15and y=0.002 to 0.20.
 14. A catalyst according to claim 11 wherein A islithium.
 15. A catalyst according to claim 11 wherein C is magnesium.16. A catalyst according to claim 11 wherein A is lithium and C ismagnesium.
 17. A catalyst according to claim 8 wherein A is lithium, Bis selected from the group consisting of titanium, tantalum and mixturesthereof and C is magnesium.
 18. A catalyst according to claim 8 whereinx=0.05 to 0.15 and y=0.002 to 0.20.
 19. A catalyst according to claim 8wherein A is lithium.
 20. A catalyst according to claim 8 wherein C ismagnesium.
 21. A catalyst according to claim 8 wherein A is lithium andC is magnesium.